This invention concerns machine tools particularly apparatus for grinding piece parts and other components to a very high accuracy, particularly but not exclusively components which have complex shapes and forms.
Due to force exerted on a workpiece, the worktable and workpiece supporting structures of such machines, distortions and misalignments occur. These result in inaccuracies in the dimensions and shape of the final machined article.
Where the dimensional errors are of the same order as the accuracy to which the article is to be machined it is impossible reliably to machine the article.
Distortions, misalignments and other error producing effects which can arise and tend to be cumulative must therefore be reduced to a level which is such that the magnitude of the cumulative error in the final article is much less than the error which can be permitted therein.
One of the primary controlling parameters in a machining operation is the accuracy with which the workpiece position relative to a machining tool is known. This parameter has been addressed and solutions proposed in our co-pending applications Nos. (our references C421.01/L, C422.01/L) filed concurrently herewith. Other factors affecting accuracy are addressed in copending applications Nos. (our references C424.01/L, C425.01/L and C426.01/L).
As a result of incorporating the refinements described and claimed in our copending applications it is possible to construct a machine tool capable of machining to very high accuracies. If however the workpiece that is to be machined is not in a stable condition, the accuracy of the machining process will be wasted.
It is an object of the present invention to provide a machining environment and a method of preparing workpieces for machining, which permits the advantages of such a machine to be realised.
The invention is of particular application to a cylindrical grinding machine.
U.S. Pat. No. 2,330,168 and German Patent publication No DE-U-8903723 both disclose machine locations in which workpieces are stored in a machine enclosure prior to working.
This invention concerns a machining location for machining workpieces, comprising:
(a) a machine tool;
(b) an enclosure for said machine tool that encloses the entire machine tool within a predetermined space;
(c) workpiece storage within said predetermined space for storing workpieces at least prior to being worked on by said machine tool and for subjecting such workpieces when so stored to said machining environment to become oriented thereto.
According to one aspect of the invention, the enclosure is mounted and supported to be separate from and independent of said machine tool so that vibrations are not transmitted from said enclosure to said machine tool.
According to another aspect of the invention, there are provided ambient environment controls for effecting control of at least the temperature of the air within said predetermined space.
Conveniently said ambient environment controls maintain the temperature of fluids following use thereof in said machine tool to a constant temperature plus or minus 0.05 degrees centigrade before they are recirculated.
The fluids in question may comprise water, oil, coolant and combinations thereof.
In a preferred embodiment said ambient environment controls includes means for circulating said fluids through paths separate for each type of fluid, and subject at least some of the fluids circulated through such paths first to heating to a desired heated temperature and then to cooling to a desired cooled temperature.
The invention is of particular application to a grinding machine particularly one which is adapted top grind to accuracies of less than one micron.
In such an application the ambient environment controls may to advantage also control the humidity within the machining environment.
The invention also lies in a method of preparing a workpiece to be machined, comprising the steps of;
(a) providing a machine tool;
(b) providing an enclosure about said machine tool to enclose said machine tool with a predetermined space; and
(c) storing one or more workpieces within said predetermined space for a predetermined period of time prior to subjecting such workpieces to being machined by said machine tool.
Preferably the workpieces are supported in the enclosure so as to be separate from and independent of said machine tool and said enclosure.
The method also includes the step of controlling the ambient environment within said predetermined space.
Typically this involves the step of controlling the temperature of the air within the enclosure.
It may also include the step of controlling the temperature of fluids utilised by said machine tool.
Preferably the temperature control of the said fluids involves controlling the said temperature to plus of minus 0.05 degrees centigrade.
The step of controlling said fluid temperatures preferably includes circulating said fluids through independent fluid paths, heating each such fluid to a given heated temperature at a predetermined location in its fluid path and thereafter cooling each such fluid to a given cooled temperature at a predetermined location in its fluid path.
The invention also lies in finished workpieces when machined by the machine tool located in the machining location as described herein after preliminary workpiece conditioning by storage in said location for a predetermined period of time.
The invention also lies in an enclosure for a machine tool which encloses the entire machine tool within a predetermined space thereby to create a machining location for machining workpieces comprising a plurality of housing shells sealingly joined together to form the enclosure some of said shells including windows through which different parts of the machine can be viewed and some including openable doors to give access to the enclosure and at least one of the housing shells including workpiece support means on which workpieces can be located prior to being machined to permit the workpieces to become conditioned by exposure to the environment within the enclosure for a predetermined period of time.
Ambient environment controls are preferably provided controlling at least the temperature of the air in the predetermined space within the enclosure.
The support means in the enclosure typically comprises shelves adapted by means of apertures to permit workpieces to be stacked vertically.
The housing shell containing the support means for storing the workpieces advantageously includes an openable door to give access to the workpiece storage area and the same housing shell or an adjoining housing shell includes window means to enable workpieces located within the workpiece storage housing to be viewed.
A machining location as described herein may to advantage include a mezzanine floor on which the enclosure is mounted, which surrounds the machine tool but is spaced therefrom, a foundation below the mezzanine floor on which the machine is supported, and partition means located below the mezzanine floor to close the gap between the underside of the mezzanine floor and the solid foundation on which the machine tool is mounted to form with the foundation and the enclosure an enclosed space.
The machining location may further comprise extractor fan means, an air inlet, air filter means associated therewith, air heating means, air humidity controlling means and air cooling means, all cooperating to control the temperature and humidity of the air within the enclosure, the filter preventing the ingress of dirt and dust into the enclosure.